Stevens in U.S. Pat. No. 4,000,739 discloses a hemostasis cannula comprising a body having a passage therethrough adapted to receive a catheter and a pair of juxtaposed gaskets mounted in the passage. The first gasket forms a seal around a catheter enclosed within the cannula. The second gasket is compressed against the first to seal the passage when the catheter is removed. The cannula also features a flexible entrance to and a port for introducing fluids into the patient's blood vessel.